The seller delivers the goods to the buyer, not cleared for import, and not unloaded from any means of transport at the named place of destination. The seller bears the costs and risks involved in bringing the goods thereto, as well as any 'duty' for import in the country of destination. (Duty refers to any customs formalities, payment for such, customs duties, taxes and any other charges.)
Whilst EXW represents the seller's minimum obligation, DDP represents the maximum.
OK - you've agreed the selling price, but now the customer turns round and says he wants you to ship the goods all the way to his flat in Karachi and pay for all the carriage, insurance, duty etc he can think of. Use DDP - it's the notional opposite of EXW where you would have the minimum obligation.
DDP is not be used where the seller is unable either directly or indirectly to obtain the import licence.
However, if the seller's obligation to meet all costs payable on import of the goods (eg VAT - value added tax) this should be made clear by adding explicit wording to the contract.
If both parties wish the buyer to bear the import duties, then DDU should be used.
DDP may be used for any mode of transport but when delivery is to take place in a port of destination on board a vessel or on the quay (wharf), the DES or DEQ terms should be used.